This invention relates to closures, in particular to manually-operated closures, conventionally in the form of a lid or cap, which may be used to keep the contents of a container from contamination or to prevent spillage, and which can be easily operated to close or open the container manually.
A very wide variety of closure types is known. One type which has achieved widespread commercial success for decades is the so-called “screw cap”. The container is provided with a rim of generally cylindrical shape on the outside of which are one or more threads. The cap is provided with an internal thread with a series of projections which may engage with a thread, particularly with a number of short thread sections distributed evenly about the periphery of the rim. Screw cap bottles, canisters and jars are widely used for containing liquids and solid materials.
Desirable features of a closure are that it should be straightforward to operate, both when closing a container, using the closure and when removing it when access to the contents or filling the container with content is required. A common requirement in numerous practical applications is that the closure should act to seal the opening on to which it is screwed and this is conventionally achieved by way of a resilient liner or ring of resilient material which, when the closure is applied and screwed down, is urged to seal against the edge of the usually circular aperture on the container itself.
As well as screw closures, a wide variety of press-fit or snap-on lid closures are known. These are not applied by rotation, but rather the closure or lid has some form of formation on it, usually at or near its edge, which is shaped to engage a corresponding formation on the rim of the container itself. In order to secure a reasonably tight connection between the closure and the container, one or both are conventionally made of a resilient material, for example a resilient plastics material.
Hybrid closures are also known where closure may be effected for example by pressing a lid with a skirt of resilient material on to a neck ring at the top of a glass container, with formations on the interior of the skirt engaging underneath formations on the neck ring. By the provision of appropriate camming surfaces, the skirt may be caused to move outwards if the closure is twisted relative to the container itself in such a fashion that the inter-engagement between the skirt and the neck ring is removed and the closure can then be lifted off. Such “snap-to-fit” and “twist to remove” lids have been used on jars for foodstuffs, such as soluble coffee solids granules, for some time.
A further type of closure is a so-called bayonet closure. In such a closure, a cylindrical wall and a skirt on the cylindrical cap have a space between them and, on the inside of the skirt and the exterior of a ring on the container, there are two or more projecting members which can be inter-engaged one with another, the extent of projection generally being slightly less than the radial gap between the skirt on the lid and the ring on the container. One of the projecting members is a generally hook-shaped projection and the other a bead or the like which can engage in the hook-shaped projection.
Such closures conventionally rely on pressing the lid and container axially together, with compression of a compressible member between the lid and the ring on the container, and then twisting the lid on the container to bring the projections and hooks into alignment. Once the pressure on the lid is removed, the compressible member urges the bead to fit into the hook, so preventing the lid from coming off. To release the lid, it is simply pressed down and turned in the opposite direction to enable the projecting members to be freed from the hooks, whereafter the lid can simply be taken off. Examples of such bayonet cap closures are disclosed in GB 1383865 and GB 1282077.